Contents lists available at ScienceDirect Psychiatry Research journal homepage: www.elsevier.com/locate/psychres Cardiac biomarkers of disordered eating: A case for decreased mean R wave amplitude Melinda Green a, ⁎ , Abigail Herrick a , Emily Kroska b , Shuhan Reyes a , Elisabeth Sage a , Linden Miles a a Cornell College Eating Disorder Institute, 600 First Street SW, Mt. Vernon, IA 52314, USA b University of Iowa Department of Psychological and Brain Sciences, W311 Seashore Hall, Iowa City, IA 52242, USA ARTICLE INFO Keywords: Cardiac biomarkers Eating disorders Mean R wave amplitude ABSTRACT The purpose of this study was to identify cardiac biomarkers of disordered eating. Mean R wave amplitude (mV), mean T wave amplitude (mV), QRS interval (sec), QTc interval (sec), and Tpeak-Tend interval (sec) were as- sessed via electrocardiography among women with clinical (n = 53) and subclinical (n = 56) eating disorder symptoms versus asymptomatic controls (n = 32). QRS and QTc intervals were significantly longer and mean T and R wave amplitudes significantly lower among women with clinical symptoms compared to asymptomatic controls. QTc interval length was significantly longer and mean R wave amplitude was significantly lower among women with subclinical symptoms versus asymptomatic controls. Decreased mean R wave amplitude yielded a comparable effect size as QTc when differentiating between asymptomatic and subclinical groups and a larger effect size than QTc when differentiating between asymptomatic and clinical groups, representing a promising clinical biomarker. 1. Introduction The National Institute of Mental Health (NIMH) launched the Research Domain Criteria Project (RDoC) to identify “clinically ac- tionable biomarkers for psychiatric disorders” in order to provide reli- able and valid biological indicators to 1) improve diagnostic accuracy, 2) more effectively identify and target high risk groups for intervention, and 3) systematically assess treatment outcomes (Insel, 2014, pg. 395). Existing research indicates clinical and subclinical eating disorder po- pulations exhibit disorder-related cardiac changes which escalate with symptom progression and ameliorate with effective treatment (Green et al., 2017; Green et al., 2016; Jáuregui-Garrido and Jáuregui-Lobera, 2012; Panagiotopoulos et al., 2000; Ülger et al., 2006). Preliminary findings suggest cardiac biomarkers represent promising diagnostic indicators of symptom severity and treatment response. Biomarkers which distinguish asymptomatic, subclinical, and clin- ical eating disorder populations are important for diagnostic, research, and treatment purposes. In the diagnostic realm, eating disorder pa- tients often inaccurately report symptoms, height, or weight due to poor insight or treatment ambivalence (McCabe et al., 2000). A bio- marker which reliably denotes symptom severity would provide an objective indicator with significant diagnostic utility. In the research realm, demand characteristics lead to inaccurate self-reporting of symptoms (McCambridge et al., 2012). Reliable biomarkers may represent better indicators of treatment and prevention outcomes in clinical trials compared to self-report methodology. In the treatment realm, biomarkers which fluctuate systematically with symptom progression could serve as clinical indicators of recovery status and treatment prognosis. Promising biomarkers should be easily assessed with relatively low costs in order to be of maximal clinical utility. Cardiac biomarkers assessed via brief electrocardiography meet these criteria. Also in the treatment realm, research on cardiac bio- markers may inform cardiac-related care for eating disorder patients. Subtle cardiac changes occur early in eating disorder progression (Green et al., 2016) and vary systematically with symptom changes (Green et al., 2017; Ülger et al., 2006). Disorder-related cardiac changes become more pronounced as symptoms worsen. Adverse car- diac events are among the leading causes of mortality and morbidity among eating disorder patients. Increased understanding of disorder- related cardiac biomarkers is essential for good clinical care (Jáuregui- Garrido and Jáuregui-Lobera, 2012; Takimoto et al., 2008). Taken together, findings suggest cardiac biomarkers show great potential among eating disorder populations. These considerations highlight the importance of identifying which cardiac biomarkers most reliably differentiate eating disorder symptoms. Several candidate electrocardiograph (ECG) biomarkers have received support including QTc interval prolongation, QRS interval prolongation, decreased mean T wave amplitude, Tpeak-Tend (Tp-e) interval prolongation, and https://doi.org/10.1016/j.psychres.2018.12.162 Received 31 July 2018; Received in revised form 3 December 2018; Accepted 29 December 2018 ⁎ Corresponding author. E-mail address: mgreen@cornellcollege.edu (M. Green). Psychiatry Research 272 (2019) 555–561 Available online 30 December 2018 0165-1781/ © 2018 Elsevier B.V. All rights reserved. T